Carbon fiber reinforced plastics (CFRP) are a material in which highly carbon fibers are highly filled in a generic plastic and have significantly improved rigidity compared to plastic alone. Since CFRP has a rigidity which can substitute for a metal, it is already beginning to be used in fuselages of airplanes and automobile bodies etc and has achieved significant weight reduction thereof. Recently, CFRP has spread to uses such as automotive parts and sporting goods. Therefore, further improvement of the mechanical properties of CFRP is required.
For example, CFRP mixed with glass fiber (GF) or carbon fiber (CF) in polyamide 6 containing clay is described in S. Wu, F. Wang, C. M. Ma, W. Chang, C. Kuo, H. Kuan, W. Chen, Mater Lett. 49 (2001) 327. In S. Wu, F. Wang, C. M. Ma, W. Chang, C. Kuo, H. Kuan, W. Chen, Mater Lett. 49 (2001) 327, when mixing glass fibers or carbon fibers in polyamide 6 containing 3% of montmorillonite as clay, tensile strength and modulus of elongation improve with increasing content of the glass fibers or carbon fibers. However, a resin containing clay has a heat resistance of about 240° C. to 250° C. and cannot be applied to parts that require further heat resistance.
On the other hand, a polyamide resin composition containing carbon particles and a swelling fluorine mica-based clay mineral layered silicate is disclosed in Japanese Laid Open Patent No. 2008-150400. The swelling fluoroine mica-based clay mineral has a high heat resistance compared to clay and can be processed at 300° C. or more. However, the content of carbon particles in the polyamide resin composition disclosed in Japanese Laid Open Patent No. 2008-150400 is 0.5 to 10 parts by mass, and for example, chopped carbon fibers (chopped CF) which are shortened cannot be applied to a process for highly filling into plastic. In CFRP, since uniformity in the dispersion state of the carbon fibers is significantly reduced when the filling amount of the carbon fiber is more than 40 wt %, ductility which is a feature of the plastic and formability is not only significantly lost but the smoothness of the surface material is also lost. Therefore, while maintaining the desired stiffness as a whole system, a technology to evenly disperse the carbon fibers and which does not degrade the performance of the plastic is required.